Excess low-frequency flux noise in dc SQUIDS incorporating Nb/AIOXIDE/Nb Josephson junctions
✍ Scribed by Martin E. Huber; Michael W. Cromar
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 230 KB
- Volume
- 165-166
- Category
- Article
- ISSN
- 0921-4526
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✦ Synopsis
We have fabricated thin-film dc SQUIDS (Superconducting Quantum Interference Devices) incorporating Nb/Al-Oxide/Nb tunnel junctions. The spectral density of the voltage noise, Sv, of stripline SQUIDS is characterized between 1 Hz and 2000 Hz. responsivi ?% aV/acP) over a significant ran
In this frequency range, Sv is proportional to the square of the a 7 pH SQ I B e of bias conditions with an unusual frequency dependence. In , the spectral density of the lux noise, SQ, at 1 Hz is less than lo-11 @$/Hz, where @, E h/2e. The observed noise does not appear to be environmental; also, it is independent of the value of the junction shunt resistance and whether the stripline material is a Pbln alloy or Nb. Subject to the constraint of a constant product of the junction area, critical current density, and SQUID self-inductance in the SQUIDS studied, Sm is inversely proportional to the junction area.